Reciprocating internal combustion (IC) engines are known for converting chemical energy stored in a fuel supply into mechanical shaft power. A fuel-oxidizer mixture is received in a variable volume of an IC engine defined by a piston translating within a cylinder bore. The fuel-oxidizer mixture burns inside the variable volume to convert chemical energy from the mixture into heat. In turn, expansion of the combustion products within the variable volume performs work on the piston, which may be transferred to an output shaft of the IC engine.
Variations in the temperature of an oxidizer stream entering an engine are known to affect engine performance. For example, heat exchangers may be used to cool an oxidizer stream to increase engine power, increase engine efficiency, or both, especially when the engine includes a compressor to boost the pressure of the oxidizer upstream of the variable volume. Such intake heat exchangers may effect thermal communication between the oxidizer stream and a flow of ambient air or a flow of engine coolant, for example. Alternatively, a fluid, such as liquid water, may be injected into the oxidizer stream to cool the oxidizer stream by evaporation therein.
U.S. Pat. No. 8,091,359 (the '359 patent), entitled “Exhaust Heat Recovery for Engine Heating and Exhaust Cooling,” purports to address the problem of higher emissions and energy losses such as viscous energy losses due to a relatively cool temperature of fluids during cold starts of an internal combustion engine. The '359 patent describes heating intake air via a gas-to-gas heat exchanger, the gas-to-gas heat exchanger being in communication with exhaust gases, and heating a fluid which flows through the engine with the intake air via a gas-to-liquid heat exchanger.
However, intake air is only drawn through the gas-to-gas heat exchanger of the '359 patent when the engine is operating without pressure boost from the compressor. Accordingly, there is a need for an improved engine intake systems and methods for operating engine intake systems to address the aforementioned problems and/or other problems in the art.